Abstract: The present disclosure relates to: a flexible joint connecting device used for sequentially coupling precast concrete segments so as to construct an underwater tunnel; an underwater tunnel construction method using the flexible joint connecting device so as to join, in a watertight manner, tunnel modules and integrally connect same, thereby constructing the underwater tunnel; and the underwater tunnel constructed by the construction method.

Abstract: A method of installing segmental concrete filled tube members. The prefabricated segmental concrete filled tube member has a hollow pipe filled therein with concrete, and a connection flange shaped in a ring radially extending from the peripheries of both ends of the pipe, wherein the segmental concrete filled tube member is integrally connected with another adjacent segmental concrete filled tube member by the connection flange.

Abstract: Disclosed is a steel-concrete composite beam. The steel-concrete composite beam has an asymmetric I-section steel member having an upper flange, a lower flange and a web. The web is formed with at least one opening at a predetermined interval. The upper flange has a narrower width than the lower flange. A pair of C-section steel members is attached integrally to the lower flange of the asymmetric I-section steel form a first space filled with concrete. The concrete interlocks with the lower flange. A deck is supported on the C-section steel members. At least one transverse reinforcing bar of slab is arranged through the opening perpendicular to the asymmetric I-section steel. An upper concrete slab is poured with the concrete to be formed at a predetermined thickness. The concrete fills in a second space defined by the C-section steel members and the lower flange so that the upper flange of the asymmetric I-section steel is embedded.